Process of producing holes with reduced openings



Aug- 1965 B. KEEGAN ETAL PROCESS OF PRODUCING HOLES WITH REDUCED OPENINGS Filed April 17, 1962 PODEf/CK 6- Mac was QMW rli'l'Qf/YEY United States Patent 3,201,856 PRQCESS 9F PRQDUCING HOLES WITH REDUCED OIPENINGS liarclay Keegan, Glasgow, and Roderick C. MacKenzie, East Kilhride, Scotland, assignors to The International Nickel Company, Inc, New York, N .Y., a corporation of Delaware Filed Apr. 17, 1962, Ser. No. 188,197 Claims priority, application Great Britain, Apr. 20, 1961, 14,323/ 61 7 Claims. ((31. 29-156-8) The present invention relates to the production of metallic objects having holes therein and, more particularly, to the production of metallic turbine structures having cooling passages therein.

A known kind of process for the production of a blank for a turbine or compressor blade with cooling passages extending longitudinally through it comprises making holes in a billet, filling them with rods of a material having properties of flow similar to those of the billet, deforming the billet to a blank with consequent elongation of the filled holes and finally removing the filler to leave the holes as the cooling passages. In practice, the holes are made in the billet by drilling and so are of uniform cross section throughout their length. Normally, such uniformity of cross section is desirable. In some blades, however, the tip section is exceptionally thin and in order to obtain a passage of substantial cross section in the main body of the blade, it is necessary to reduce the area of the cross section of the passage in the tip region. In other blades it is necessary for the passages to be of smaller cross-sectional area close to the root, and even over a substantial length from the root, than at the tip. Broadly, it may be necessary to make the cross-sectional area of a passage vary over its length. Although attempts were made to provide a simple process for producing blades and other turbine structures having cooling passages of non-uniform cross-sectional area, none, as far as we are aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that by means of a particularly controlled sequence of operations, a remarkably simple process for the production of metallic objects having internal passages of complex cross-sectional sizes can be provided.

It is an object of the present invention to provide a novel process for the production of metallic objects having internal passages of non-uniform cross-sectional area.

Another object of the invention is to provide a novel process for the production of turbine structures having internal passages of non-uniform cross-sectional area.

The invention also contemplates providing a novel process for the production of fluid-cooled turbine blades having internal passages of non-uniform cross-sectional area.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawing in which:

FIGURES l, 2, 3 and 4 are cross-sectional views of filled metallic masses or billets employed in the process of the present invention; and FIGS. 1A, 2A, 3A and 4A are cross-sectional views of worked structures produced from the masses of FIGS. 1, 2, 3 and 4, respectively, by the use of the process of the present invention.

According to this invention, the resistance to deformation of the billet presented by the filler rods is reduced over a length from one end of a billet with the result that under substantially uniform deformation forces the crosssectional area of the deformed filled holes becomes less over that length than over the remaining length of the holes. If the passages should be smaller at the tip, the resistance to deformation usually need be reduced over a short length of filler rod only.

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Usually, if it is necessary to vary the cross-sectional area of any of the final holes over their length at all, it is necessary so to reduce the area of all of them. Naturally, however, if the shape of the blade is such that some of the holes can be of uniform across section throughout their length, the invention is employed only in the production of the remaining holes.

The deformation is most conveniently effected by extrusion. If the billet is only partially extruded so as to leave in the extrusion container a length of billet which is to form the root of the blade and the passages should be smaller at the tip, the resistance to deformation of the billet is, of course, reduced at the end that leads during the extrusion. If the billet is extruded as completely as possible so as to provide an extruded product that after removal of a short length of the trailing end is of uniform cross section throughout its length, the resistance to deformation may be reduced from either end of the billet.

The preferred way of reducing the resistance to deformation is to fill one length of each hole only incompletely. Thus, over this length each filler rod may be drilled to provide an internal cavity concentric with the outer Wall of the rod; or a slot may be cut in each rod from the end; or a length of the rod may be made frusto conical instead of cylindrical. In each case, the metal of the billet will fill the resultant cavity and the final pas sage will be reduced in cross section in accordance with the reduction in the cross-sectional area of the filler rod. The extent to which this area can be reduced is limited by the risk of cracking and depends in part upon the composition of the billet. With a billet of nickel-chromium-cobalt alloy (18% to 21% chromium, 15% to 21% cobalt) containing aluminum and titanium and of the kind commonly used in gas turbines, the maximum permissible reduction in area is not more than about 60%. With a nickel-chromium-cobalt-molybdenum alloy billet for use at higher service temperature (13.5% to 16% chromium, 18% to 22% cobalt, 4.5% to 5.5% molybdenum) and containing aluminum and titanium, the maximum per missible reduction in area is not more than about 35%. If desired, the cavity in the filled hole may be filled with a particulate material, e.g., aluminia, the proportion of voids in this material then determining the shape of the final passage. Such a particulate material may be kept in place by a weld deposit over the end of the hole. The use of a particulate material may be beneficial when the incompletely filled hole is in the root metal and the exclusion of air is desirable to keep irregularities to a minimum.

Another way of reducing the resistance to deformation is to use a length of filler rod of weaker material than that of the remaining length. For instance, the latter length may be an iron-manganese-titanium alloy as described in US. Patent No. 2,941,281 and the former length may be mild steel.

The process of the present invention is particularly described in reference to the drawing. Referring now thereto, FIGURES 1 to 4 show billets 11 of heat resistant metal having at least one hole 12 of uniform cross-sectional area extending therethrough which hole 12 is at least partly filled with filler body 13. Filler body 13 is positioned in hole 12 so that an ascertained zone of enhanced flowability is present in hole 12. For example, in FIG. 1, the ascertained zone of enhanced flowability is provided by void 14 in filler body 13 extending from leading end 15. After working by extrusion and removal of filler body 13, passage 16 of non-uniform cross-sectional area in turbine blade 17 is produced as shown in FIG. 1A. Likewise, in FIG. 2, void 14 provided by employing partly tapered filler body 13 is the zone of enhanced flowability. When billet 11 is extruded with end 18 trailing, the passageway in the root (d FIG. 2) closes to.( d FIGFZA) and is smaller than the original; hole,

this closure is brought about by the flow of rnetal'near the radius of the extrusion die. This is useful where the finished root shape 17 is very slim. The zone of enhanced flowability can be a non-compacted mass of ceramic particles'19 as shown in FIG. '3 or it can be a relatively weak metalbody, e.g.,*rnild steel, such as shownt at in FIG. 4. *The configuration of passage 16 in worked-metal 21 resulting from the extrusion of billets 11 of FIGS. 3 and 4 and removal of the filler body therefrom are shown in FIGS.- 3A and- 4A, respectively.

The present invention is particularly applicable to the production of hollow'fluid cooled turbine blades,

cooled nozzle guide vanes, and foramin-ous components -15 for rocket motors made from'heat resistant metal.

With respect to the manufacture of turbineblades by a means of the novel process, it should be understood that' the term heat resistant metal is used to include austenitic nickel-chromium alloys, including 'nickel-chromium iron and nickel-chromium -cobalt and cobalt-chr'omium alloys, including cobalt-tehromium-iron alloys, which .con tain a total of at-least about nickel plus chromium, cobalt plus chromium or nickel plus chromium plus cobalt (i.e.,a total of at least about 25 of chromium plus nickel and/or cobalt) in addition to small amounts of tantalum, silicon, manganese, zirconium and boron which may optionally be present 'in the alloys.

to be subjected in use to temperatures up to about 700 C. or above and, accordingly,must be but worked at tem- The balance 7 'of the alloys, if any, is iron. These alloys are adapted stantially uniform deformation'forces to induce flow of I said metallic mass and said filler body and thereafter removing said fillerybody from the thus worked metallic mass to open the thus-produced passage of controlled non-uniform cross-sectional area.

2. A process as set forth in claim 1 wherein at least one hole of 'substantially uniform cross section in the V metallicmass is filled only incompletely with a filler body extendingthroughout the length of the hole.

3; A'process as set forth in claim 2 wherein particulatematerial is provided in an incompletely filled portion of the hole.

a 4. A process as set forthiin claim 1 wherein at least one hole of substantially, unifiorm cross section in the metallic mass isgco-rnpletely filled throughout the length with filler rod and in which aplength of the filler rod is of weaker material than that'of the remaining length 7 I of filler rod and fills theezoneof-enhanced flowability.

5. A processfor producing a worked heat resistant metalobject having a plurality of passages of controlled nonruniformity'of cross-sectional area which comprises providing a billet of heat resistant metal having a plurality 7 aluminum, titanium, molybdenum, tungsten, niobium,

of holes of substantially uniform cross section therein, at least partly filling said holes with a filler body extending throughout the length of said holes and having reduced resistance to deformationrover only a portion of the a length of said holes to 'provide at least one ascertained peratures around 1200 C. Fillers such'as the aforementioned iron-manganese-titanium alloy and mild steel can be conveniently removed from the heat resistant metal byselective dissolution in an aqueous solution of a common mineral acid.

Although the present invention has been describe'd in, conjunction with' preferred embodiments, it is to be Zone of enhanced flowability in each'of said holes and also at least one predetermined zone of flowability less than the flowability of the zone of enhanced flowability in reach of said holes, working-the billet together with said filler body by extrusion to inducev flow of said heat resistant metal ancl said filler body'and thereafter removing said filler body from .the thus-worked heat resistant metal to opeuthe thus-produced passages'of controlled non-uniform cross sectional area V a J 6. A process as defined in claim -5 wherein the heat resistant'metal object'isa turbine'blade' andv the zone of enhanced 'flowablity is of cross-sectional area which comprisesproviding a metallic mass having at least'one hole of substantially uniform cross section, therein, at least partly filling said hole with a filler body extending throughout the length of said hole, and having reduced resistance to deformation over only a portion of the length thereof, to provide at least one predetermined zone of enhanced flowability and at least one predetermined zone of flowability less than the flow ability. of the zone of enhanced flowability,-working the metallic mass together with said filler body under subof enhanced flowability is adjacent the the billet during -extrusion.*

7. A process as, defined in claim 5 wherein the heat resistant metal object is a turbine blade and the zone in the root metal of the billet leading edge of during extrusion.

I References Citedby the Examiner UNITED STATES PATENTS 2,047,555 7/36 Gardner -1 T29j]156.8r 2,093,775 9/ 37 ColwellQ 2,948,052 8/60 Kubera 29 -423 X 2,970,368 '2/61 Home 29-1568 2,972,806 2/61 Higuctt et 8.1. 29-1568 2,986,806 6/61 Hignett et al. 29-156.8 3,044,153 7/62 Kent etal. 29-156.8

WHITMORE WILTZ", Primary Examiner; 

1. A PROCESS FOR PRODUCING A WORKED METALLIC OBJECT HAVING AT LEAST ONE PASSAGE OF CONTROLLED NON-UNIFORMITY OF CROSS-SECTIONAL AREA WHICH COMPRISES PROVIDING A METALTIC MASS HAVING AT LEAST ONE HOLE OF SUBSTANTIALLY UNIFORM CROSS SECTION THEREIN, AT LEAST PARTLY FILLING SAID HOLE WITH A FILLER BODY EXTENDING THROUGHOUT THE LENGTH OF SAID HOLE AND HAVING REDUCED RESISTANCE TO DEFORMATION OVER ONLY A PORTION OF THE LENGTH THEREOF, TO PROVIDE AT LEAST ONE PREDETERMINED ZONE OF ENHANCED FLOWABILITY AND AT LEAST ONE PREDETERMINED ZONE OF FLOWABILITY LESS THAN THE FLOWABILITY OF THE ZONE OF ENHANCED FLOWABILITY, WORKING THE METALLIC MASS TOGETHER WITH SAID FILLER BODY UNDER SUBSTANTIALLY UNIFORM DEFORMATION FORCES TO INDUCE FLOW OF SAID METALLIC MASS AND SAID FILLER BODY AND THEREAFTER REMOVING SAID FILLER BODY FROM THE THUS-WORKING METALLIC MASS TO OPEN THE THUS-PRODUCED PASSAGE OF CONTROLLED NON-UNIFORM CROSS-SECTIONAL AREA. 